Metal heating method and apparatus



, March 21, 1933. J. J. MOLAUGHLIN METAL HEATING METHOD AND APPARATUSFiled May 9, 1932 2 Sheets-Sheet l INVENTOR Jbkn J/l/ Zing/2162iATTGRNEY METAL HEATING METHOD AND APPARATUS Filed May 9, 1932 I 2Sheets-Sheet 2 ATTORNEY Patented Mar. 21, 1933JOHN.J'OSEPH..MCLAU'.GHLIN, OF NORTH TQTNAWANDAjNEW YORK mar-AL HEATING-.METHOD AND APPARATUS.

1 Applicationiled May 9, 1932. Serial No. 610,058.

My present invention concerns metal heating apparatus of the-type shownin Patents Nos, 1,243,44234.and1,302,843. These pat.- ents relate toprogressively heating a contin- 5 -uous length of metal while feeding itautomatically into, through and outof a furnace in such manner as tomaintain an endless supply of hot metal for use inautoma-tic machinesadapted to forge spikes, screws, bolts, nuts', or

0 the like.

Preferably, the blanks are as long as obs tai-nable and, where thebundle coils are used, successive coils may be electrically welded endto end to maintain a continuous unbroken length of material progressingthrough the furnace and to the forging machine. Effective heating toforgingtemperature requires that the metal passing through thefurnacebe'kept freely exposed on al-lsides to high heat for aconsiderable time. To :do this with metal passing straight through thefurnace would require either a very slow feed or a very long furnace,whereas it is desirable to use the relatively small compact furnace andto give the metal a desired highrate of feed into and out of the furnacecombined with a relatively slow rate. of progress through the furnace.Consequently, it has been a common practice to bend the metal in more or.less open loops idisposed transversely to the adirection of feedthrough the furnace, adjacent loops being maintained in orderly relationby sliding them along a metal support.

In said patents, particularly Nos. 1,243,442

I and 1,302,843, this involves bending the material so .as to give it .apredetermined initial shape and .setin the curvature of an open coil orhelix of desired diameter and length, suitable for the stiffness of thematerial and the size of the furnace.

By suitably predetermining the length, form and arrangement of theinterior support and the number of turns of the helix for travel ofeachturn through the furnace may be as long as necessary. Hence, it ispossible to maintain the required rate of output of heated materialwhile using a relatively small, compact furnace.

hanging thereon, the length of time required Because ofthe efi'ec't ofthe heat upon the coiled material softening it, it is necessary tocarefully control the rates of movement of the metal at the supply endand the exit end,

so that it will be-unwoundfrom the exit end i of the helix by the timeit has become softened to the proper degree and before it becomes toosoft to maintain proper separation of the turns of the helix.

It has also been proposed to b end themetal .in other shapes for'slidingit through the furnace, but in all cases, so far as I am aware, it hasbeen found necessary to water-cool the support along which the metalslides, and the cold support cools the part of .the metal .in

vcontact therewith, with theresult that itis vdelivered to the forgingmachine having some portions of its length substantiallycooler andtherefore harder than others. For this reason, it has been the practiceto make the furvnace temperatures very high in order to properly heatthe parts that are subject to cooling by contact with thewater-cooledhanger; and

as maybe inferred from the specifications of some of said patents, suchhigh temperatures make it difiicult to prevent theuncooled parts of thecoil from becoming .too soft to maintain proper separation of the turnsof. .thehe- .lix. or from becoming softened to the welding point.

During many years of practical experience in large quantityproduction'of bolts and the like, according to the above hightemperature method of operation, the soft metal, high temperatures andwater-cooled hanger were:

supposed to be necessary, and more 'thancompensated for by the ease withwhich highly heated, relatively soft iron can be shaped in the forgingmachine; but more recently I began to appreciate more fully theobjectionable features; that the high temperature involves great wasteof heat, particularly by heat losses through the walls of the furnace;makes it more diflicult to maintain the desired non-oxidizingtemperature in the furnace; o and makes it more diificult to avoid scaleformation on the hotter parts of the metal, resulting in an undesirablepercentage of inferior product in the forging machine.

So I have "made certain observations and experiments, and as a result Ihave discovered that the forging machines, even though they may requiremore power, can be made to operate successfully on metal which is of 5 amuch lower temperature, and correspondingly harder; that the resultingforged articles are superior; that the correspondingly lower temperaturerequired for thefurnace eliminates danger of scale formation and makesit a relatively simplematter to maintain a non-oxidizing atmosphere.Secondly and incidentally, I have discovered that this lower range ofuseful metal temperatures is low enough so that the water cooling of thehanger may be entirely dispensed with; that thus the hanger is permittedto assume the temperature of the hot gases in the furnace. Third, thatcontrary to expectation, the hot hanger does not have the effect ofproducing arrangement 'of mechanical parts. somewhat for preferably,somewhere between that and as. concerns the forging machines; and thathot, over-heated, over-soft spots on the parts of the coil in contacttherewith. That is to say, by the new method, the heat-impartingtemperature-drop from the hot hanger metal to the fully heated coilmetal in contact therewith, is enormously less than was the heat-"abstracting drop from heated coil to the water-cooled hanger and thecoil metal in contact therewith. Moreover, the hot hanger that isimparting heat to the part of the coil in contact therewith, is at thesame temperature as the hot gases that are in contact with the remainderof the coil. Fourth: Experiment shows that temperatures near 1530 F 1200F. for the.iron,'are entirely practical temperatures substantially,above 1530 F. are practical as concerns metals available forhangersthat'are'not water-cooled. An ample margin of safetyisattainableby making the hanger of certain varieties of stainless steel of lowcarbon content containing large percentages of chromium, say 17% "withnickel, from 8% to 10% to 19%, or preferably 25% to 26%. Such metalswill notgbecome soft or sticky, and in fact will afford exceptionallylow frictional resistance to the sliding of the coiled metal along thesame.

Having thus explainedmy new method,

the details for practicing] it may be more fully understood from thefollowing description inconnection with the drawings, in which Fig. l isa vertical central section through a furnace showing the novelconstruction of the apparatus, in combination with the fea- ..tureswhich are old.

F ig 2 is. a horizontal section throughthe furnace walls disclosinga-plan' view of the mandrel, hanger and coilsof material which are beingheated. 7

These figures show a furnace, and general like those of Figs. 3 and 1},respectively, of Patent'No. 1,302,813, except that the parts whereby thecoil material is set in the proper curvature and fed into the furnace.are omitted. Such mechanism may be the same or different from that ofsaid patent, the essential novelty of the apparatus residing in thecombination with the furnace of the novel hanger and the novel method ofoperating the furnace in connection therewith.

. The furnacein which the materialis heat- .ed is shown as including areverberatory chamberl adapted to be maintained at desired temperaturesby a non-oxidizing atmosphere of flaming gases and products ofcombustion. The functions of the fire brick regenerator shown at 4 neednot be described s nce these parts are only such as are commonlyemployed in regenerative reverberatory furnaces. The sidewalls 5, 6 andthe end wall 7 are sloped inward to the bottom of the furnace so as tobring them closer to the helical coil which is to be heated thereby butwithout danger of contact'therewith. The heating chamber within thefurnace is of suitable dimensions to provide for a helix 53, 54:. Thmandrel 19 does not require cooling. Q

' Extending forward from the uppermost portion of the annular mandrel 19is a hanger 25 in suitable relation for receiving the successive helicalturns of the material and for holding them freely suspended and exposedto the beaten all sides. The hanger com- 'prises a U-shaped memberwhichextends to about the middle of, the heating space and thedlstance fromits freeendto the exit opening is such that a loop of the helix whendrawn off of the end will have space enough to hang in an open loopwithout danger of drawing a kink.

In the present case,'the successive turns of the helix are caused toslide along the hanger by having the hangerslope downward for abouttwo-thirds of its length, downward sliding being facilitated by gravity,the resiliency of the helix and also by slight vibration imparted byoperation of associated machinery.

Because of the new method employed, the hanger 25 is preferably of solidrod or bar material; or, if a pipe is used, it is not watercooled; also,the sides of the'U are preferjably parallel, ;there being no necessityfor shifting points of contact with the coil, be-

cause by the new method the hanger is approximately as hot as thehighest heat to be imparted to the coil. Furthermore, the material notbeing heated to sticky or welding temperature by the new method, thereis no danger of forming a loop by welding contact of adjacent loops, asPatent 1,302,843 says might happen in operating by the old method.Consequently, as shown in Fig. 1, the inclination of hanger 25 is suchthat when successive loops are pushed free of mandrel 19, they slidedown almost to the center of the furnace,'where a short length of themandrel is substantially horizontal. So most of the loops being heatedcan be concentrated at this relatively central point in the furnacecavity. The free end of the hanger 25 curves upward quite abruptly, thegreater stiffness of the material due to the lower heat, making itdesirable to have a sharp upturn of the hanger at this point in orderthat the coils may be drawn off one at a time, and only when the pull ofthe forging machine feed makes this necessary.

The exit opening through which the material is withdrawn isapproximately in line with one side of the helix of heated material andon the level of the top of said helix. The side which it is on isselected with reference to the direction of winding of the helix so thatthe successive turns will be drawn straight off endwise with minimumrecurving tendency. This means that if the helix is wound in thedirection of a left-hand screw, the exit opening will be at the upperlefthand side of the furnace.

The circular interior of the mandrel is formed so as to support thelining of firebrick 19a adapted to protect the exterior sup portingparts from the interior heat and at the same time to furnishreverberatory heating surface for the interior of the furnace.

By suitable mechanism, as, for instance, that described in the priorpatent, a sufiicient number of turns of the helix are deposited on thehanger and the free end brought out through the exit opening.

The number of turns and the speed of operation will be governed withrespect to the heat of the furnace and the size of the material so thatthe material will be properly heated by the time it reaches the end ofthe hanger.

At the rear of the furnace is a door 110 through which the helicalmaterial may be manipulated either initially or during operation. At theside of the doorway is a laterpeated. It will be evident, however, thatin ly different apparatus for bending and transversely feeding along asupport in a furnace, a continuous supply of hot, rod-like material foruse in hot forging'machines or the like.

I claim 1. In apparatus for heating continuous lengths of rod-like metalfor forging and the like, a reverberatory furnace and an un-- cooledsupport therein, arranged for sliding the rod-like material along thesame in small area contact therewith, the uncooled support being ofmetal having a softening point higher than the intended temperature of aheating medium in the furnace and approximating the higher forgingtemperatures for the rod-like metal.

2. In the art of heating continuous lengths of rod-like metal which hasbeen formed in loops adapted for suspension from and sliding along ametal support in a furnace, a method of uniformly heating the metal tohot-forging temperature, which includes employing as the material forthe support, a

metal which softens at a substantially highmissible and adequate byreason of the above described heating of the support.

Signed at North Tonawanda, in the county of Niagara and State of NewYork, this 5th day of May A. D. 1932.

J ()HN JOSEPH MoLAUGI-ILIN.

ally and downwardly extending slot 112 in which the rod material may beinserted laterally. The portion of the slot unfilled by the rod iscovered by the pivoted, gravity latch 113.

The operation of this specific apparatus,

for practice of my new method as above described, is obvious, and neednot be here re-

